<!DOCTYPE html>
<html>
<head>
  <title>默认封面</title>
  <style>
    body {
      margin: 0;
      padding: 0;
      width: 100%;
      height: 100vh;
      display: flex;
      align-items: center;
      justify-content: center;
      background: linear-gradient(135deg, #e0f7fa 0%, #80deea 100%);
      color: white;
      font-family: Arial, sans-serif;
      font-size: 2rem;
      text-align: center;
    }
  </style>
</head>
<body>
  默认封面
</body>
</html> 